Method and device for handling a mooring line

ABSTRACT

A method of handling a mooring line having a first end portion attached to a vessel comprises capturing a second end portion of a mooring line with a moveable arm mounted to a towboat. The method also comprises securing a mid-portion of the mooring line between the first end portion and the second end portion with respect to the towboat. The method further comprises moving the second end portion of the mooring line from a first position to a second position whilst the mid-portion of the mooring line is secured to the towboat.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No. PCT/EP2020/070008, filed Jul. 15, 2020, which claims priority to Danish Application No. PA201900878 filed Jul. 15, 2019, under 35 U.S.C. § 119(a). Each of the above-referenced patent applications is incorporated by reference in its entirety.

BACKGROUND Field of the Invention

The present invention relates to a method and device for handling a mooring line.

Description of the Related Technology

In some terminals the quay is shorter than the length of the vessel. This means that the vessel cannot be moored directly to the quayside along the entire length of the vessel. This is often the case for oil tankers or liquid natural gas tankers where the vessel is moored in a small bespoke terminal or service platform. In such cases, the vessel is moored to a central quay or service platform but also moored to additional smaller adjacent satellite offshore mooring structures which may be called “mooring dolphins” and “breast dolphins”.

The smaller satellite offshore mooring structures can be set back from the central quay. This means that when the hull of the vessel is adjacent to the central quay, the bow and stern of the vessel are not adjacent to the smaller offshore mooring structures.

In some cases, there may be a large distance between the bow or stern of the vessel and the smaller satellite offshore mooring structure. This means that the mooring line cannot be passed or thrown down from the vessel to the quayside. In this case the mooring line must be physically moved by a towboat from the vessel to the satellite offshore mooring structure.

A problem with passing the mooring line down to the towboat is that the mooring line must be manually thrown from the deck of the vessel onto the towboat. This can be difficult, and the crew member may take several attempts to successfully place the mooring line close enough to the towboat for the mooring line to be picked up by the towboat. In some cases, the mooring line is caught with a boat hook by a crew member on the towboat. If the mooring line enters the water, then in some circumstances the weight of the mooring line will increase making its line handling harder.

A known tugboat is shown in NL1010650 which describes a tugboat using a hook connected to a towline and the hook is mounted on a boom for catching a light line hanging from a vessel. The hook catches the light line and when the light line is drawn back up to the vessel, the tow line is drawn up to the vessel and attached to the vessel. The arrangement shown in NL1010650 is for managing tow lines and requires passing the tow line up to the vessel which increases the line handling time. This arrangement is not suitable for line handling of mooring lines.

In the present invention there is provided a method of handling a mooring line having a first end portion attached to a vessel comprising: capturing a second end portion of a mooring line with a moveable arm mounted to a towboat; securing a mid-portion of the mooring line between the first end portion and the second end portion with respect to the towboat; and moving the second end portion of the mooring line from a first position to a second position whilst the mid-portion of the mooring line is secured to the towboat.

Optionally, the capturing comprises grasping the second end portion suspended from the deck of the vessel.

Optionally, the securing comprises positioning the mid-portion of the mooring line in a securing mechanism fixed with respect to the hull of the towboat.

Optionally, the method comprises moving the mid-portion of the mooring line from a position outside a perimeter of the towboat to a position inside the perimeter of the towboat before securing the mid-portion of the mooring line.

Optionally, the moveable arm moves the second end portion and the mid-portion of the mooring line at the same time.

Optionally, the moveable arm is rotatable or slidable with respect to the towboat.

Optionally, the moveable arm is rotatable about an arc of substantially 180 degrees with respect to the towboat.

Optionally, the method comprises towing the tow line or the mooring line with the towboat after the mid-portion of the mooring line is secured to the towboat.

Optionally, the method comprises presenting the second end portion of the mooring line for handling once the second end portion of the mooring line is moved into the second position.

Optionally, the second end portion of the mooring line is presented for manual handling by a person on the shore.

Optionally, the method comprises slackening the mooring line between the second end portion and the secured mid-portion.

Optionally, the slackening comprises moving the moveable arm coupled to the second end portion of the mooring line towards the secured mid-portion.

Optionally, the tension between the first end portion of the mooring line and the secured mid-portion is greater than the tension between the secured mid-portion and the second end portion of the mooring line.

Optionally, the moveable arm is telescopic.

Optionally, the method comprises displaying an image of the moveable arm to an operator of the moveable arm.

Optionally, the method comprises providing feedback to an operator of the moveable when the moveable arm successfully grasps the second end portion of the mooring line.

Optionally, the mid-portion of or the mooring line is fixed with respect to the towboat in front of a propulsor of the towboat.

Optionally, the method is carried out autonomously by a towboat controller or manually by an operator of the towboat.

In a second aspect of the invention there is provided a line handling device for handling a mooring line having a first end portion attached to a vessel comprising: a moveable arm mounted on a towboat and arranged to capture a second end portion of a mooring line; a securing mechanism mounted to the towboat and arranged to secure a mid-portion of the mooring line between the first end portion and the second end portion with respect to the towboat; wherein the moveable arm is arranged to move the second end portion of the mooring line from a first position to a second position whilst the mid-portion of the mooring line is secured to the towboat.

In another aspect of the invention there is provided a towboat comprising a line handling device according to the second aspect.

The invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of a terminal according to an example;

FIGS. 2, 3 and 4 show a side view of the towboat handling the line according to an example;

FIG. 5 shows a cross-sectional front view of the towboat along the line A-A according to an example;

FIG. 6 shows a schematic view of the towboat according to an example; and

FIG. 7 shows a flow diagram of the line handling method according to an example.

DETAILED DESCRIPTION

FIG. 1 shows a perspective view of a terminal 100 for mooring a vessel 102. The vessel 102 can be any type of vessel such as an oil tanker, an LNG tanker, a container ship, a bulk carrier ship or any other vessel which can be moored at a terminal. The terminal 100 comprises a central quay or service platform 104 extending out from the shore 106 via a pier structure 108. The terminal 100 further comprises smaller satellite offshore mooring structures 110, 112 connected to the central quay 104 via catwalks 122, 124. In some examples, the satellite offshore mooring structures 110, 112 are called “breast dolphins” or “mooring dolphins”. However, the offshore mooring structures can be any suitable arrangement for mooring the vessel 102. Hereinafter the term “offshore mooring structures” will be used.

The smaller satellite offshore mooring structures 110, 112 are set back from the central quay 104. In this way, when the vessel 102 is adjacent to the central quay 104, there is clear water between the stern 114 and the bow 116 of the vessel 102 and the smaller satellite offshore mooring structures 110, 112. In some examples, the distance between the smaller satellite offshore mooring structures 110, 112 and the vessel 102 is between 20 m to 90 m. In some examples, the mooring lines 118, 120 are between 35 m and 75 m. In some other examples, the mooring lines 118, 120 are between 45 m and 65 m. In some other examples the mooring lines 118, 120 are approximately 55 m. In some examples, the distance between the smaller satellite offshore mooring structures 110, 112 and the vessel 102 is greater than half the beam B (as shown in FIG. 1) of the vessel 102.

This means that first and second mooring lines 118, 120 are transported between the vessel 102 and the smaller satellite offshore mooring structures 110, 112. The first and second mooring lines 118, 120 are transported from the vessel 102 to the smaller satellite offshore mooring structures 110, 112 because the distance between the vessel 102 and the smaller satellite offshore mooring structures 110, 112 is too far to manually throw the first and second mooring lines 118, 120.

In some other examples, the first and second mooring lines 118, 120 are transported from the vessel 102 to the shore 106 (rather than to the smaller satellite offshore mooring structures 110, 112). In this example, the bow 116 and the stern 114 of the vessel 102 are moored to the shore 106 via the first and second mooring lines 118, 120. In this way, in some examples, the terminal 100 optionally does not comprise the smaller satellite offshore mooring structures 110, 112.

FIG. 1 shows the first and second mooring lines 118, 120 for the vessel 102 used for mooring the vessel 102. However, in other examples, there can be additional mooring lines for mooring the vessel 102 to the central quay 104 and additional smaller satellite offshore mooring structures 110, 112. In addition, further mooring lines can be provided mooring the vessel 102 to the shore 106.

In some examples, a towboat 200 is used to handle the mooring line 118, 120. The towboat 200 is arranged to move between the vessel 102 and the smaller satellite offshore mooring structures 110, 112 whilst towing the first and/or the second mooring lines 118, 120. The towboat 200 will now be discussed in further detail with respect to the other Figures.

FIG. 2 shows a cross sectional side view of the towboat 200 and the vessel 102. The towboat 200 is arranged to handle the mooring lines 118, 120 and transport them to the smaller satellite offshore mooring structures 110, 112 or the shore 106 as required.

The examples described below are made in reference to a towboat 200. However, in other examples, the towboat 200 can be any other types of vessel that require line handling of mooring lines for other vessels 102. Hereinafter, the term “towboat” will be used in reference to the line handling method, but the towboat can be any type of suitable vessel for carrying out line handling of mooring lines.

Furthermore, the examples described below are made with respect to mooring lines 118, 120. However, the line handling method is applicable to any lines, wires or ropes which require handling during mooring.

FIG. 2 shows the towboat 200 before handling the mooring line 120 at the bow 116 of the vessel 102. For the purposes of clarity, only part of the vessel 102 is shown in FIG. 2. The surface 202 of the water is shown in FIG. 2 and represented by the dotted line.

Whilst FIG. 2 shows the towboat 200 positioned at the bow 116 of the vessel 102, the position of the towboat 200 with respect to the vessel 102 is illustrative and the towboat 200 can be in any position relative to the vessel 102 for the purpose of handling the mooring line 120.

As shown in FIG. 1, a first smaller satellite offshore mooring structure 110 is used to tether the stern 114 of the vessel 102 with a first mooring line 116. Likewise, a second smaller satellite offshore mooring structure 112 is used to tether the bow 116 of the vessel 102 with a second mooring line 120. In other examples, the first and second mooring lines 118, 120 can be attached to any suitable location on the vessel 102.

The first and second mooring lines 118, 120 are attached to the vessel 102 via bollards, capstans or any other suitable fastening arrangement (not shown in FIG. 2).

The mooring line 120 as shown in FIG. 2 comprises a first end portion 212 which is attached to the vessel 102. A second end portion 214 of the mooring line 120 is suspended from the bow 116 of the vessel 102 ready for capture by the towboat 200. In between the first end portion 212 and the second end portion 214 is a mid-portion 216 of the mooring line 120. The mid-portion 216 of the mooring line 120 is configured to be secured to the towboat 200 during the line handling operation. This will be discussed in further detail below. The mid-portion 216 of the mooring line 120 can be any part of the mooring line 120 between the first end portion 212 and the second end portion 214.

In some examples, the second end portion 214 of the mooring line 120 comprises a loop or an eye 218. The loop or eye 218 is arranged to be placed over a bollard 400 or capstan or other stationary structure. In some other examples, the second end portion 214 of the mooring line 120 does not comprise a loop 218 and the second end portion 214 is tied to a bollard 400 (as shown in FIG. 4). FIG. 4 shows a cross sectional side view of the towboat 200 and the vessel 102 where the towboat 200 is adjacent to a quay or mooring structures such as the satellite offshore mooring structures 110, 112.

The towboat 200 will now be discussed in further detail with reference to FIG. 2.

The towboat 200 comprises a hull 204 and at least one fender 206 mounted to the hull 204. The fender 206 projects outwardly from the hull 204 so that the towboat 200 can safely engage the vessel 102 or the quayside. In this way, the towboat 200 can thrust against the side of the vessel 102 and the at least one fender 206 between the vessel 102 and the hull 204 of the towboat 200 prevents damage to either the vessel 102 or the towboat 200.

In some examples, the towboat 200 comprises a circumferential fender 206 which is mounted on the perimeter 500 (best shown in FIG. 5) of the hull 204. FIG. 5 shows a cross sectional view of the towboat 200 across the axis A-A.

In some alternative examples, the fender 206 can be a plurality of fenders 206 which are arranged around the perimeter 500 of the hull 204. The fender 206 as shown in FIG. 2 is a compressible rubber tube mounted on the gunwale of the towboat 200. In other examples, the fender 206 is a plurality of compressible objects such as rubber tyres (not shown). Optionally, in some examples, the at least one fender 206 can be omitted.

The towboat 200 comprises at least one propulsor 208 mounted to the hull 204.

In an example, the towboat 200 comprises a plurality of propulsors 208, 302 (the two propulsors 208, 302 side by side are best shown in FIG. 5) for providing propulsion to the towboat 200. FIG. 2 shows a single propulsor 208, but further propulsors are provided. In some examples, the propulsor 208 is an azimuth thruster 208. In some examples, the towboat 200 has two propulsors 208, 302. In some examples, the propulsors 208, 302 of the towboat 200 are configured to generate a thrust having a bollard pull of at least 2 tonnes.

In this way, the towboat 200 is able to pull the mooring line 120 with sufficient thrust to transport the mooring line 120 between the vessel 102 and the smaller satellite offshore mooring structures 110, 112. In some embodiments, the towboat is configured to pull a mooring line 120 having a weight per meter between 1 Kg to 20 Kg. In one example the mooring line has a weight per meter of 10 kg. In this way, the towboat can pull a 100 m mooring line weighing 100 kg to 2000 Kg.

In some examples, the plurality of propulsors 208, 302 are azimuthing thrusters which can rotate about a vertical axis to direct thrust in a plurality of directions. Some azimuthing thrusters are azimuthing podded drives which are also known as “azipods”. Hereinafter, azimuthing podded drives will be referred to as azimuth thrusters. The other propulsor 302 (not shown in FIG. 2 but shown in FIG. 5) is located adjacent and parallel to the first propulsor 208. In some other examples, one or more propulsors 208, 302 can use the Voith principle. In some other examples (not shown) there can be three or more propulsors.

In an example, the at least one propulsor 208, 302 is one or more of: a propeller, a thruster, a rudder propeller, an electric rudder propeller, a fixed pitch propeller, a variable pitch propeller, an azimuthing thruster, a water jet propulsor, or an azimuthing podded drives thruster. In another example, the at least one propulsor are bow thrusters. As mentioned previously, the at least one propulsor 208, 302 are mounted at the stern 210 of the towboat 200 however, in other examples additionally or alternatively the at least one propulsor 208, 302 can be mounted to the hull 204 elsewhere e.g. at the bow 224 of the towboat. In other examples, the at least one propulsor 208, 302 can be any means suitable for providing propulsion to the towboat 200.

In some examples, the at least one propulsor 208, 302 is coupled to and driven by a first primary mover 600 (as shown in FIG. 6). FIG. 6 shows a schematic representation of the components of the towboat 200. In some examples, the first primary mover 600 can be a diesel engine, electrical motor, or a diesel-electric hybrid system. The diesel engine can be a 4-stroke diesel engine or a 2-stroke diesel engine. In other examples, the engine 600 is an internal combustion engine that can burn any type of fossil fuel. In some examples, the first prime mover 600 can be any suitable means for powering the at least one propulsor 208, 302.

The towboat 200 comprises a wheelhouse 222 mounted on the deck 502 and/or the hull 204. The wheelhouse 222 comprises the towboat operational controls of the towboat 200. The thrust and heading of the towboat 200 are controlled from the wheelhouse 222 by the captain of the towboat 200 with wheelhouse controls 602 (as shown in FIG. 6). Manoeuvring of the towboat 200 from a wheelhouse 222 is well known and will not be discussed any further for the purposes of brevity.

The captain can further control other operational features of the towboat 200 for carrying the line handling method which will be discussed in further detail below. In some examples, the wheelhouse 222 is optional and the control of the towboat 200 is autonomous or controlled remotely from the shore 106. Remote controlled and autonomously controlled tugboats are described in Danish patent applications PA 201670186 and PA 201670185 which are herein incorporated by reference. The controller 608 as shown in FIG. 6 is configured to carry out autonomous or remote control of the towboat 200. No further discussion of autonomous or remote control of the towboat 200 will be made for the purposes of brevity.

The line handling method and device will now be discussed in further detail. The towboat 200 comprises a line handling device 220 for handling the mooring line 120. The line handling device 220 is arranged so that the mooring line 120 can be handled remotely by the captain in the wheelhouse 222 or remotely by another person. In some examples, the remote operation of the line handling method is carried out on shore and not by a person on the towboat 200

By providing remote line handling, this means that a deckhand does not have to stand on the deck 502 and be potentially hit with the mooring line 120 which has been thrown down from the vessel 102. This means that the deckhand can be carrying out other safer tasks whilst the mooring line 120 is being handled by the line handling device 220. Accordingly, the line handling device 220 improves the safety and efficiency of the crew on the towboat 200.

FIG. 2 shows the line handling device 220 mounted to the towboat 200. The line handling device 220 can be mounted to the hull 204 or the deck 502 of the towboat 200. The towboat 200 is in a configuration such that the line handling device 220 is positioned ready to couple the mooring line 120 to the line handling device 220 and the towboat 200.

The line handling device 220 comprises a moveable arm 226 moveable between a plurality of positions. In some examples, the moveable arm 226 is pivotable about pivot 228 which is mounted to the towboat 200. The moveable arm 226 in some examples is pivotable through an arc of substantially 180 degrees. In this way, the moveable arm 226 can move from a stern position on the towboat 200 to a bow position on the towboat 220. The pivotable movement of the moveable arm 226 is shown in FIG. 2 with the curved dotted arrow C. Whilst FIGS. 2 and 3 show the moveable arm 226 moving from stern to bow, in other examples the moveable arm 226 is pivotable through other directions such as from a port side to a starboard side of the towboat 200.

Optionally, the moveable arm 226 is moveable along the longitudinal axis B-B of the moveable arm 226. In this way, the moveable arm 226 can extend its reach. For example, the moveable arm 226 can extend its reach beyond the perimeter 500 of the towboat 200 towards the suspended mooring line 120. In some examples, the moveable arm 226 is telescopic and the moveable arm 226 is extendable along the longitudinal axis B-B of the moveable arm 226.

In some examples, the moveable arm 226 is extendable with other mechanisms other than a telescopic mechanism such as a folding mechanism (not shown). Alternatively, or additionally, the moveable arm 226 is foldable and the moveable arm 226 comprises a hinge or pivot (not shown) in the middle of the moveable arm 226 such that the moveable arm 226 can extend the reach of the moveable arm 226.

The line handling device 220 comprises at least one actuator 230 coupled to the moveable arm 226 for moving the moveable arm 226 between different positions (for example between the stern position and the bow position shown in FIGS. 2 and 3 respectively). The at least one actuator 230 as shown in FIG. 2 is a hydraulic cylinder 230 mounted on the deck 502 or hull 204 causing pivotal movement of the moveable arm 226. The hydraulic cylinder 230 is coupled to a hydraulic system 604 (as shown in FIG. 6). The hydraulic system 604 is powered by the engine 600 or a separate hydraulic genset (not shown) and drives various functions which are hydraulically powered on the towboat 200. In some examples, control of the hydraulic system 604 can be carried out from the wheelhouse controls 602.

The telescopic movement of the moveable arm 226 is hydraulically actuated in some examples. Likewise, additional hydraulic actuators (not shown) are coupled to the moveable arm 226 and the hydraulic system 604 for extending the telescopic parts of the moveable arm 226. The moveable arm 226 as shown in FIG. 2 is partially extended beyond the perimeter 500 of the towboat 200. The moveable arm 226 can be fully retracted within the perimeter 500 of the towboat 200. When the moveable arm 226 is fully retracted, the movable arm can be safely positioned and stowed away for sailing.

In some examples, the moveable arm 226 can be extended well beyond the perimeter 500 of the towboat 200. In some examples the moveable arm 226 extends fully to a reach of 15 meters or 10 meters or 7 meters or 5 meters or 2 meters or 1 meter beyond the perimeter 500 of the towboat 200.

In some examples (not shown), the moveable arm 226 is mounted on a rotatable base so that the movable arm 226 is rotatable about the axis A-A. In this way, the moveable arm 226 is moveable from a port side of the towboat 200 to a starboard side of the towboat 200. In some other examples, the moveable arm 226 is not mounted on a rotatable base and the moveable arm 226 is moved in a port direction or a starboard direction by manoeuvring the towboat 200.

In other examples, the moveable arm 226 is coupled to an electric motor mounted at the pivot 228 for causing the pivotable movement of the moveable arm 226. In other examples, the moveable arm 226 can be slidably mounted on rails (not shown) for moving the moveable arm 226 with respect to the hull 204 of the towboat. The rails are mounted to the deck 502 of the towboat 200. Accordingly, the moveable arm 226 can optionally slide rather than pivot with respect to the towboat 200. In some examples, the moveable arm 226 is slidable and pivotable with respect to the deck 502 of the towboat 200.

The line handling device 220 comprises a gripper 232 for capturing the second end portion 214 of the mooring line 120. In an example, the gripper 232 comprises a pair of jaws 234 configured to move between an open and a closed position. The pair of jaws 234 are configured to surround and grip the second end portion 214 of the mooring line 120 when the pair of jaws 234 are in the closed position. When the pair of jaws 234 are in the closed position, the second end portion 214 is physically coupled to the gripper 232 and the mooring line 120 can be handle remotely. In some examples, the gripper 232 is connected to the hydraulic system 604 and can be remotely operated from the wheelhouse controls 602.

In some examples, the gripper 232 does not comprise a pair of jaws 234. Instead the gripper 232 is a hook for hooking the loop 218 in the second end portion 214. In some examples, the gripper 232 is any suitable mechanism or device for physically engaging the second end portion 214 of the mooring line 120.

In some examples, the gripper 232 is mounted and fixed to the end of the moveable arm 226. In other examples, the gripper 232 is optionally rotatably mounted on the end of the moveable arm 226 such that the gripper 232 can rotate about the axis B-B. Rotation of the gripper 232 can be carried out by a servo (not shown) or a hydraulic actuator coupled to the hydraulic system 604.

Movement of the moveable arm 226 in reference to the line handling method will be discussed in further detail below.

As the towboat 200 approaches the vessel 102, the moveable arm 226 is optionally extended beyond the perimeter 500 of the hull 204 of the towboat 200. In this way, the moveable arm 226 telescopically extends towards the suspended second end portion 214 of the mooring line 120. In other embodiments, the moveable arm 226 is not telescopic or extendible and the moveable arm 226 is pivoted into a suitable position for grasping the second end portion 214.

As mentioned previously, the movement and control of the moveable arm 226 and the gripper 232 is controlled from the wheelhouse controls 602. In some examples, the operator of the moveable arm 226 can see the moveable arm 226 and the gripper 232 from the wheelhouse 222. However, in other examples, the moveable arm 226 is obscured from view due to equipment mounted on the deck 502. In some examples, the operator of the moveable arm 226 receives status information of the moveable arm 226 if the operator cannot see the moveable arm 226 during operation.

In some examples, there is at least one sensor 504 providing feedback information of the status of the moveable arm 226 and/or the gripper 232. Indeed, in some embodiments, there is at least one camera 504 mounted on the moveable arm 226 providing a field of view including the gripper 232. The feedback camera 504 is shown in FIGS. 5 and 6. The images from the camera 504 may be displayed on a display 610 mounted in the wheelhouse 222. In this way, the operator of the moveable arm 226 can still view the moveable arm 226 and the gripper 232 during operation.

In some examples, there is additionally other sensors for determining the status of the moveable arm 226 and/or the gripper 232. In some examples, there can be a force sensor (not shown) on the gripper 232 to determine that the gripper 232 has successfully gripped the mooring line 120. Additionally or alternatively, there may be one or more other sensors for determining the presence of the mooring line 120 in the gripper 232. For example, the gripper 232 may comprise an optical sensor, another camera, a proximity sensor, an ultrasound sensor, or any other suitable sensor for determining the presence of the mooring line 120 between the pair of jaws 234.

Optionally, in some examples, the at least one sensor 504 for providing feedback information sends a signal to the controller 608. In dependence of receiving the feedback information from the at least one sensor 504, the controller 608 sends information to display 610 to the operator that the mooring line 120 is in the correct position to be gripped by the gripper 232.

Optionally, the controller 608 can send a control signal to the hydraulic system 604 and the gripper 232 and/or moveable arm 226 to secure the mooring line 120. The controller 608 can be of a pure software character and include programming instructions described herein for detection of input conditions and control of output conditions, illustrated in FIG. 6 and discussed herein. The programming instructions can be stored in a memory of controller 608, not shown. In some examples, the programming instructions correspond to the processes and functions described herein. The controller 608 can be executed by a hardware processor. The programming instructions can be implemented in C, C++, JAVA, or any other suitable programming languages. In some examples, some or all of the portions of the controller 608 can be implemented in application specific circuitry such as ASICs and FPGAs.

In other examples, the operator has a clear line of sight from the wheelhouse 222 to the gripper 232. In this case, the camera 504 is not needed because the operator can see when the mooring line 120 is between the pair of jaws 234. The position of moveable arm 226, the gripper 232 and/or the towboat 200 may be adjusted so that the second end portion 214 of the mooring line 120 is positioned within the pair of jaws 234.

Once the second end portion 214 of the mooring line 120 is between the pair of jaws 234, the operator or the controller 608 actuates the gripper 232. This means that the second end portion 214 of the mooring line 120 is captured by the moveable arm 226 mounted to the towboat 200 as shown in step 700 in FIG. 7. FIG. 7 shows a flow diagram of the line handling method.

Once the gripper 232 has captured the second end portion 214 of the mooring line to the moveable arm 226, the mid-portion 216 of the mooring line 120 is secured with respect to the towboat 200 as shown in step 702 in FIG. 7.

The operator or the controller 608 sends a control signal to the hydraulic actuator 230, to move the moveable arm 226. Turning to FIG. 3, the moveable arm 226 can be seen in the bow position wherein the moveable arm 226 is positioned towards the bow 224 of the towboat 200. The hydraulic actuator 230 is fully extended such that the moveable arm 226 pivots from a stern position to a bow position.

The moveable arm 226 pivots about the pivot 228 and rotates substantially 180 degrees with respect to the towboat 200. In order to allow the moveable arm 226 to pivot substantially 180 degrees with respect to the towboat 200, the wheelhouse 222 is optionally offset to one side of the deck 502 as shown in FIG. 5. In some other embodiments, the wheelhouse 222 is centrally positioned on the deck and the moveable arm 226 does not pivot through the same amount of angular rotation. Accordingly, when the moveable arm 226 is in the bow position, the moveable arm 226 rests on the wheelhouse 222.

In order for the towboat 200 to tow the mooring line 120, the mooring line 120 must be secured to the towboat 200.

A securing mechanism 300 is provided to secure the mid-portion 216 of the mooring line 120 to the towboat 200. Providing an additional securing mechanism 300 better secures the mooring line 120 to the towboat 200.

Comparing FIGS. 2 and 3, pivoting the moveable arm 226 between the stern position and the bow position causes the mid-portion 216 of the mooring line 120 to move from a position outside a perimeter 500 of the towboat 200 (as shown in FIG. 2) to a position inside the perimeter 500 of the towboat 200 (as shown in FIG. 3). Once the mid-portion 216 of the mooring line is inside the perimeter 500 of the towboat 200, the mid-portion 216 can be secured to the towboat 200 with the securing mechanism 300.

In some examples, when the moveable arm 226 moves the second end portion 214 and the mid-portion 216 the mooring line 120 at the same time. This means that the second end portion 214 can be moved to the bow position and the mid-portion 216 can be moved to the securing mechanism 300 in the same single movement. This means that further movement of the moveable arm 226 may not be needed before the mooring line 120 is secured by the securing mechanism 300.

The securing mechanism 300 will now be discussed in further detail with respect to FIGS. 3 and 5. The securing mechanism 300 is mounted to the hull 204 or the deck 502. The securing mechanism 300 is positioned in front of the propulsors 208, 302 on the towboat 200. This means that the towboat 200 is easier to steer when towing the mooring line 120.

The securing mechanism 300 comprises line grippers 508, 510 which are positioned either side of the mid-portion 216 of the mooring line 120. The line grippers 508, 510 exert a force on the mid-portion 216 on the mooring line 120 so that the mooring line 120 is fixed with respect to the securing mechanism 300 and the towboat 200. In this way, when the mid-portion 216 of the mooring line 120 is fixed in the securing mechanism 300, the tension in the mooring line 120 is exerted on towboat 200 via the securing mechanism 300.

In some examples, the line grippers 508, 510 are moveable between a gripping position and a released position. The securing mechanism 300 in some examples is coupled to the hydraulic system 604 and the controller 608. In this way, a control signal from the wheelhouse controls 602 causes the line grippers to move from a released position to a gripping position. The securing mechanism 300 can comprise a plurality of grippers for increasing the friction on the mid-portion 216 on the mooring line 120 without exerting a shearing force which could cut the mooring line 120.

In some examples, the securing mechanism 300 comprises a force sensor for determining the force exerted on the mid-portion 216 of the mooring line 120. The force sensor 612 sends a signal to the controller 608. In some examples, if the controller 608 determines from the signal that the force on the mid-portion 216 exceeds a force threshold, then the controller 608 can issue a warning to the operator. Alternatively, or additionally, the controller 608 can fully or partially release the line grippers 508, 510 to prevent the mooring line 120 being cut.

Optionally the securing mechanism 300 comprises a line guide 512. The moveable arm 226 is configured to drag the mooring line 120 once captured by the gripper 232 over the securing mechanism 300 and between the line guides 512.

The line guides 512 are positioned on either side of an opening 514 which comprises the line grippers and the mid-portion 216 of the mooring line 120. The line guides 512 are sloped such that when the mid-portion 216 of the mooring line engages the line guide 512, the mid-portion 216 is urged under its own weight to slide down the line guides 512 and in to the opening 514. In this way, as the moveable arm 226 moves from the stern position to the bow position, the mooring line 120 is passed between the line guides 512 and the mid-portion 216 will always slide down into the opening 514 and adjacent to the line grippers 508, 510.

In some examples, as shown in FIG. 5, the line grippers 508, 510 are elements which squeeze the mooring line 120 from the side along the length of the mooring line 120. However in other examples, the line grippers 508, 510 can comprise other mechanisms for gripping and securing the mooring line 120. For example, the line grippers 508, 510 can comprise a pair of scissoring arms (not shown) that overlapping and push down on the mooring line 120. In some examples, the line guides 512 alternatively, or additionally are pivotable and fold down on the mooring line 120. The opening 514 can comprise a labyrinthine path (not shown) for the mooring line 120 for increasing the friction between the securing mechanism 300 and the mooring line 120.

Once the mooring line 120 has been secured by the securing mechanism 300, the towboat 200 can tow the mooring line 120 between the vessel 102 and the satellite offshore mooring structures 110, 112.

Turning to FIG. 4, the towboat 200 is shown adjacent to the satellite offshore mooring structures 110, 112. In this way, the towboat 200 has towed the mooring line 120 approximately 50 to 100 m. The moveable arm 226 moves the second end portion 214 of the mooring line 120 from a first position P1 to a second position P2 whilst the mid-portion 216 of the mooring line 120 is secured to the towboat 200 as shown in step 704 of FIG. 7.

The moveable arm 226 moves from a fully extended position P1 as shown in FIG. 3 to a partially retracted position P2 as shown in FIG. 4. FIG. 3 shows the relative positions of the first position P1 and the second position P2 of the moveable arm 226 with dotted lines. When the moveable arm 226 retracts towards the second position P2, this moves the gripper 232 and the second end portion 214 towards the towboat 200 and the securing mechanism 300. In some examples, the moveable arm 226 retracts a predetermined distances D 1. The moveable arm 226 in some examples retracts telescopically from the first position P1 to the second position P2. Optionally, the operator can determine the distance D1 during the line handling method. In some examples, the operator may determine that the person 402 on the quay may need more slack in the second end portion 214 of the mooring line 120. The operator may then retract the moveable arm 226 closer to the securing mechanism 300.

When the moveable arm 226 has moved into the second position P2, the towboat 200 presents the second end portion 214 of the mooring line 120 for handling once the second end portion 214 of the mooring line 120 is moved into the second position P2. The towboat 200 then presents the second end portion 214 of the mooring line to a person 402 on the shore 106 for manual handling.

When the moveable arm 226 retracts from the first position P1 to the second position P2 the mooring line 120 slackens between the second end portion 214 and the secured mid-portion 216. In this way, the tension is reduced between the second end portion 214 and the secured mid-portion 216. This means that the tension between the first end portion 212 of mooring line 120 and the secured mid-portion 216 is greater than the tension between the secured mid-portion 216 and the second end portion 214 of the mooring line 120.

Advantageously this means that the person 402 handling the second end portion 214 does not have to pull against the full tension in the mooring line 120 when placing the second end portion 214 over the bollard 400. This makes handling the mooring line 120 easier for the person 402 because the towboat 200 ensures that the tension in the mooring line 120 is between the secured mid-portion 216 and the first end portion 212 secured to the vessel 102.

In other examples, two or more of the above described examples may be combined. In other examples, features of one example may be combined with features of one or more other examples. Embodiments of the present invention have been discussed with particular reference to the examples illustrated. However, it will be appreciated that variations and modifications may be made to the examples described within the scope of the invention. 

What is claimed is:
 1. A method of handling a mooring line having a first end portion attached to a vessel comprising: capturing a second end portion of a mooring line with a moveable arm mounted to a towboat; securing a mid-portion of the mooring line between the first end portion and the second end portion with respect to the towboat; and moving the second end portion of the mooring line from a first position to a second position whilst the mid-portion of the mooring line is secured to the towboat.
 2. The method according to claim 1, wherein the capturing comprises grasping the second end portion suspended from the deck of the vessel.
 3. The method according to claim 1, wherein the securing comprises positioning the mid-portion of the mooring line in a securing mechanism fixed with respect to the hull of the towboat.
 4. The method according to claim 1, wherein the method comprises moving the mid-portion of the mooring line from a position outside a perimeter of the towboat to a position inside the perimeter of the towboat before securing the mid-portion of the mooring line.
 5. The method according to claim 1, wherein the moveable arm moves the second end portion and the mid-portion of the mooring line at the same time.
 6. The method according to claim 1, wherein the moveable arm is rotatable or slidable with respect to the towboat.
 7. The method according to claim 6, wherein the moveable arm is rotatable about an arc of substantially 180 degrees with respect to the towboat.
 8. The method according to claim 1, wherein the method comprises towing the tow line or the mooring line with the towboat after the mid-portion of the mooring line is secured to the towboat.
 9. The method according to claim 1, wherein the method comprises presenting the second end portion of the mooring line for handling once the second end portion of the mooring line is moved into the second position.
 10. The method according to claim 9, wherein the second end portion of the mooring line is presented for manual handling by a person on the shore.
 11. The method according to claim 1, wherein the method comprises slackening the mooring line between the second end portion and the secured mid-portion.
 12. The method according to claim 11, wherein the slackening comprises moving the moveable arm coupled to the second end portion of the mooring line towards the secured mid-portion.
 13. The method according to claim 11, wherein the tension between the first end portion of the mooring line and the secured mid-portion is greater than the tension between the secured mid-portion and the second end portion of the mooring line.
 14. The method according to claim 1, wherein the moveable arm is telescopic.
 15. The method according to claim 1, wherein the method comprises displaying an image of the moveable arm to an operator of the moveable arm.
 16. The method according to claim 1, wherein the method comprises providing feedback to an operator of the moveable when the moveable arm successfully grasps the second end portion of the mooring line.
 17. The method according to claim 1, wherein the mid-portion of or the mooring line is fixed with respect to the towboat in front of a propulsor of the towboat.
 18. The method according to claim 1, wherein the method is carried out autonomously by a towboat controller or manually by an operator of the towboat.
 19. A line handling device for handling a mooring line having a first end portion attached to a vessel comprising: a moveable arm mounted on a towboat and arranged to capture a second end portion of a mooring line; a securing mechanism mounted to the towboat and arranged to secure a mid-portion of the mooring line between the first end portion and the second end portion with respect to the towboat; wherein the moveable arm is arranged to move the second end portion of the mooring line from a first position to a second position whilst the mid-portion of the mooring line is secured to the towboat.
 20. A towboat comprising a line handling device for handling a mooring line having a first end portion attached to a vessel comprising: a moveable arm mounted on a towboat and arranged to capture a second end portion of a mooring line; a securing mechanism mounted to the towboat and arranged to secure a mid-portion of the mooring line between the first end portion and the second end portion with respect to the towboat; wherein the moveable arm is arranged to move the second end portion of the mooring line from a first position to a second position whilst the mid-portion of the mooring line is secured to the towboat. 